Retinoic acid (RA) treatment has been used in the last decade for redifferentiation of metastatic thyroid cancer that have lost radioiodine uptake (RIup) with heterogeneous results.
Aim: To evaluate the improvement of RIup after a course of RA treatment.
Method: Retrospective analysis of 29 patients with radioiodine negative metastatic disease (17 men /12 women; 22 papillary, 4 follicular and 3 oncocytic tumours). RA was given at a dose of 0.661.5 mg/kg for 512 weeks, followed by a therapeutic 131I dose (37007400 MBq). Thyroglobulin levels and CT imaging control after 3 months of RA were performed.
Results: In 44.8% of the patients (14 out of 29 cases, 11 papillary/3 follicular) a positive radioiodine scan was observed; in 7 additional cases (5 papillary, 2 oncocytic) a weak RIup was also apparent (total responders 21/29, 72.4%), and in the remaining 8 the RIup persisted negative (6 papillary, 1 follicular and one oncocytic). No correlation was observed between changes in thyroglobulin levels and recovery of RIup. In 11 RA positive treatments a stabilization of mestastasic growth was observed in 5, while in 6 tumoural mass increased at short term. No major side effects were detected.
Conclusion: A relatively high rate of reinduction of RIup after RA treatment may be possible in advanced stage papillary and follicular thyroid cancer patients, with uncertainty in relation to a potential modification of the natural course of the disease. Further studies, aiming to identify potential responders to RA treatment by a better characterization of the biological nature of these tumours, will be required for an improved indication of RA coadjuvant treatment of thyroid cancer in the future.
28 Apr - 02 May 2007
European Society of Endocrinology